Configuration.cs

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using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Tgstation.Server.Api.Models;
using Tgstation.Server.Host.Core;
using Tgstation.Server.Host.IO;
using Tgstation.Server.Host.Security;

namespace Tgstation.Server.Host.Components.StaticFiles
{
    sealed class Configuration : IConfiguration
    {
        const string CodeModificationsSubdirectory = "CodeModifications";
        const string EventScriptsSubdirectory = "EventScripts";
        const string GameStaticFilesSubdirectory = "GameStaticFiles";

        const string StaticIgnoreFile = ".tgsignore";

        const string CodeModificationsHeadFile = "HeadInclude.dm";
        const string CodeModificationsTailFile = "TailInclude.dm";

        static readonly IReadOnlyDictionary<EventType, string> EventTypeScriptFileNameMap = new Dictionary<EventType, string>
        {
            { EventType.CompileStart, "PreCompile" },
            { EventType.CompileComplete, "PostCompile" },
            { EventType.RepoPreSynchronize, "PreSynchronize" }
        };

        readonly IIOManager ioManager;

        readonly ISynchronousIOManager synchronousIOManager;

        readonly ISymlinkFactory symlinkFactory;

        readonly IProcessExecutor processExecutor;

        readonly IPostWriteHandler postWriteHandler;

        readonly IPlatformIdentifier platformIdentifier;

        readonly ILogger<Configuration> logger;

        readonly SemaphoreSlim semaphore;

        public Configuration(IIOManager ioManager, ISynchronousIOManager synchronousIOManager, ISymlinkFactory symlinkFactory, IProcessExecutor processExecutor, IPostWriteHandler postWriteHandler, IPlatformIdentifier platformIdentifier, ILogger<Configuration> logger)
        {
            this.ioManager = ioManager ?? throw new ArgumentNullException(nameof(ioManager));
            this.synchronousIOManager = synchronousIOManager ?? throw new ArgumentNullException(nameof(synchronousIOManager));
            this.symlinkFactory = symlinkFactory ?? throw new ArgumentNullException(nameof(symlinkFactory));
            this.processExecutor = processExecutor ?? throw new ArgumentNullException(nameof(processExecutor));
            this.postWriteHandler = postWriteHandler ?? throw new ArgumentNullException(nameof(postWriteHandler));
            this.platformIdentifier = platformIdentifier ?? throw new ArgumentNullException(nameof(platformIdentifier));
            this.logger = logger ?? throw new ArgumentNullException(nameof(logger));

            semaphore = new SemaphoreSlim(1);
        }

        public void Dispose() => semaphore.Dispose();

        string StaticIgnorePath() => ioManager.ConcatPath(GameStaticFilesSubdirectory, StaticIgnoreFile);

        async Task EnsureDirectories(CancellationToken cancellationToken)
        {
            async Task ValidateStaticFolder()
            {
                await ioManager.CreateDirectory(GameStaticFilesSubdirectory, cancellationToken).ConfigureAwait(false);
                var staticIgnorePath = StaticIgnorePath();
                if(!await ioManager.FileExists(staticIgnorePath, cancellationToken).ConfigureAwait(false))
                    await ioManager.WriteAllBytes(staticIgnorePath, Array.Empty<byte>(), cancellationToken).ConfigureAwait(false);
            }

            await Task.WhenAll(ioManager.CreateDirectory(CodeModificationsSubdirectory, cancellationToken), ioManager.CreateDirectory(EventScriptsSubdirectory, cancellationToken), ValidateStaticFolder()).ConfigureAwait(false);
        }

        public async Task<ServerSideModifications> CopyDMFilesTo(string dmeFile, string destination, CancellationToken cancellationToken)
        {

            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
            {
                await EnsureDirectories(cancellationToken).ConfigureAwait(false);

                //just assume no other fs race conditions here
                var dmeExistsTask = ioManager.FileExists(ioManager.ConcatPath(CodeModificationsSubdirectory, dmeFile), cancellationToken);
                var headFileExistsTask = ioManager.FileExists(ioManager.ConcatPath(CodeModificationsSubdirectory, CodeModificationsHeadFile), cancellationToken);
                var tailFileExistsTask = ioManager.FileExists(ioManager.ConcatPath(CodeModificationsSubdirectory, CodeModificationsTailFile), cancellationToken);
                var copyTask = ioManager.CopyDirectory(CodeModificationsSubdirectory, destination, null, cancellationToken);

                await Task.WhenAll(dmeExistsTask, headFileExistsTask, tailFileExistsTask, copyTask).ConfigureAwait(false);

                if (!dmeExistsTask.Result && !headFileExistsTask.Result && !tailFileExistsTask.Result)
                    return null;

                if (dmeExistsTask.Result)
                    return new ServerSideModifications(null, null, true);

                if (!headFileExistsTask.Result && !tailFileExistsTask.Result)
                    return null;

                string IncludeLine(string filePath) => String.Format(CultureInfo.InvariantCulture, "#include \"{0}\"", filePath);
            
                return new ServerSideModifications(headFileExistsTask.Result ? IncludeLine(CodeModificationsHeadFile) : null, tailFileExistsTask.Result ? IncludeLine(CodeModificationsTailFile) : null, false);
            }
        }

        string ValidateConfigRelativePath(string configurationRelativePath)
        {
            var nullOrEmptyCheck = String.IsNullOrEmpty(configurationRelativePath);
            if (nullOrEmptyCheck)
                configurationRelativePath = ".";
            if (configurationRelativePath[0] == Path.DirectorySeparatorChar || configurationRelativePath[0] == Path.AltDirectorySeparatorChar)
                configurationRelativePath = '.' + configurationRelativePath;
            var resolved = ioManager.ResolvePath(configurationRelativePath);
            var local = !nullOrEmptyCheck ? ioManager.ResolvePath(".") : null;
            if (!nullOrEmptyCheck && resolved.Length < local.Length) //.. fuccbois
                throw new InvalidOperationException("Attempted to access file outside of configuration manager!");
            return resolved;
        }

        public async Task<IReadOnlyList<ConfigurationFile>> ListDirectory(string configurationRelativePath, ISystemIdentity systemIdentity, CancellationToken cancellationToken)
        {
            await EnsureDirectories(cancellationToken).ConfigureAwait(false);
            var path = ValidateConfigRelativePath(configurationRelativePath);

            if (configurationRelativePath == null)
                configurationRelativePath = "/";

            List<ConfigurationFile> result = new List<ConfigurationFile>();

            void ListImpl()
            {
                var enumerator = synchronousIOManager.GetDirectories(path, cancellationToken);
                try
                {
                    result.AddRange(enumerator.Select(x => new ConfigurationFile
                    {
                        IsDirectory = true,
                        Path = ioManager.ConcatPath(configurationRelativePath, x),
                    }));
                }
                catch (IOException e)
                {
                    logger.LogDebug("IOException while writing {0}: {1}", path, e);
                    result = null;
                    return;
                }
                enumerator = synchronousIOManager.GetFiles(path, cancellationToken);
                result.AddRange(enumerator.Select(x => new ConfigurationFile
                {
                    IsDirectory = false,
                    Path = ioManager.ConcatPath(configurationRelativePath, x),
                }));
            }

            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
                if (systemIdentity == null)
                    ListImpl();
                else
                    await systemIdentity.RunImpersonated(ListImpl, cancellationToken).ConfigureAwait(false);

            return result;
        }

        public async Task<ConfigurationFile> Read(string configurationRelativePath, ISystemIdentity systemIdentity, CancellationToken cancellationToken)
        {
            await EnsureDirectories(cancellationToken).ConfigureAwait(false);
            var path = ValidateConfigRelativePath(configurationRelativePath);

            ConfigurationFile result = null;

            void ReadImpl()
            {
                lock (this)
                    try
                    {
                        var content = synchronousIOManager.ReadFile(path);
                        string sha1String;
#pragma warning disable CA5350 // Do not use insecure cryptographic algorithm SHA1.
                        using (var sha1 = new SHA1Managed())
#pragma warning restore CA5350 // Do not use insecure cryptographic algorithm SHA1.
                            sha1String = String.Join("", sha1.ComputeHash(content).Select(b => b.ToString("x2", CultureInfo.InvariantCulture)));
                        result = new ConfigurationFile
                        {
                            Content = content,
                            IsDirectory = false,
                            LastReadHash = sha1String,
                            AccessDenied = false,
                            Path = configurationRelativePath
                        };
                    }
                    catch (UnauthorizedAccessException)
                    {
                        //this happens on windows, dunno about linux
                        bool isDirectory;
                        try
                        {
                            isDirectory = synchronousIOManager.IsDirectory(path);
                        }
                        catch
                        {
                            isDirectory = false;
                        }

                        result = new ConfigurationFile
                        {
                            Path = configurationRelativePath
                        };
                        if (!isDirectory)
                            result.AccessDenied = true;
                        else
                            result.IsDirectory = true;
                    }
            }

            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
                if (systemIdentity == null)
                    await Task.Factory.StartNew(ReadImpl, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current).ConfigureAwait(false);
                else
                    await systemIdentity.RunImpersonated(ReadImpl, cancellationToken).ConfigureAwait(false);

            return result;
        }

        public async Task SymlinkStaticFilesTo(string destination, CancellationToken cancellationToken)
        {
            async Task<IReadOnlyList<string>> GetIgnoreFiles()
            {
                var ignoreFileBytes = await ioManager.ReadAllBytes(StaticIgnorePath(), cancellationToken).ConfigureAwait(false);
                var ignoreFileText = Encoding.UTF8.GetString(ignoreFileBytes);

                var results = new List<string> { StaticIgnoreFile };

                //we don't want to lose trailing whitespace on linux
                using (var reader = new StringReader(ignoreFileText))
                {
                    cancellationToken.ThrowIfCancellationRequested();
                    var line = await reader.ReadLineAsync().ConfigureAwait(false);
                    if (!String.IsNullOrEmpty(line))
                        results.Add(line);
                }

                return results;
            };

            IReadOnlyList<string> ignoreFiles;

            async Task SymlinkBase(bool files)
            {
                Task<IReadOnlyList<string>> task;
                if (files)
                    task = ioManager.GetFiles(GameStaticFilesSubdirectory, cancellationToken);
                else
                    task = ioManager.GetDirectories(GameStaticFilesSubdirectory, cancellationToken);
                var entries = await task.ConfigureAwait(false);

                await Task.WhenAll(entries.Select(async x =>
                {
                    var fileName = ioManager.GetFileName(x);

                    bool ignored;
                    if (platformIdentifier.IsWindows)
                        //need to normalize
                        ignored = ignoreFiles.Any(y => fileName.ToUpperInvariant() == y.ToUpperInvariant());
                    else
                        ignored = ignoreFiles.Any(y => fileName == y);

                    if (ignored)
                    {
                        logger.LogTrace("Ignoring static file {0}...", fileName);
                        return;
                    }

                    var destPath = ioManager.ConcatPath(destination, fileName);
                    logger.LogTrace("Symlinking {0} to {1}...", x, destPath);
                    var fileExistsTask = ioManager.FileExists(destPath, cancellationToken);
                    if (await ioManager.DirectoryExists(destPath, cancellationToken).ConfigureAwait(false))
                        await ioManager.DeleteDirectory(destPath, cancellationToken).ConfigureAwait(false);
                    var fileExists = await fileExistsTask.ConfigureAwait(false);
                    if (fileExists)
                        await ioManager.DeleteFile(destPath, cancellationToken).ConfigureAwait(false);
                    await symlinkFactory.CreateSymbolicLink(ioManager.ResolvePath(x), ioManager.ResolvePath(destPath), cancellationToken).ConfigureAwait(false);
                })).ConfigureAwait(false);
            }

            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
            {
                await EnsureDirectories(cancellationToken).ConfigureAwait(false);
                ignoreFiles = await GetIgnoreFiles().ConfigureAwait(false);
                await Task.WhenAll(SymlinkBase(true), SymlinkBase(false)).ConfigureAwait(false);
            }
        }

        public async Task<ConfigurationFile> Write(string configurationRelativePath, ISystemIdentity systemIdentity, byte[] data, string previousHash, CancellationToken cancellationToken)
        {
            await EnsureDirectories(cancellationToken).ConfigureAwait(false);
            var path = ValidateConfigRelativePath(configurationRelativePath);

            ConfigurationFile result = null;

            void WriteImpl()
            {
                lock (this)
                    try
                    {
                        var fileHash = previousHash;
                        var success = synchronousIOManager.WriteFileChecked(path, data, ref fileHash, cancellationToken);
                        if (!success)
                            return;
                        if (data != null)
                            postWriteHandler.HandleWrite(path);                     
                        result = new ConfigurationFile
                        {
                            Content = data,
                            IsDirectory = false,
                            LastReadHash = fileHash,
                            AccessDenied = false,
                            Path = configurationRelativePath
                        };
                    }
                    catch (UnauthorizedAccessException)
                    {
                        //this happens on windows, dunno about linux
                        bool isDirectory;
                        try
                        {
                            isDirectory = synchronousIOManager.IsDirectory(path);
                        }
                        catch
                        {
                            isDirectory = false;
                        }

                        result = new ConfigurationFile
                        {
                            Path = configurationRelativePath
                        };
                        if (!isDirectory)
                            result.AccessDenied = true;
                        else
                            result.IsDirectory = true;
                    }
            }

            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
                if (systemIdentity == null)
                    await Task.Factory.StartNew(WriteImpl, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current).ConfigureAwait(false);
                else
                    await systemIdentity.RunImpersonated(WriteImpl, cancellationToken).ConfigureAwait(false);

            return result;
        }

        public async Task<bool> CreateDirectory(string configurationRelativePath, ISystemIdentity systemIdentity, CancellationToken cancellationToken)
        {
            await EnsureDirectories(cancellationToken).ConfigureAwait(false);
            var path = ValidateConfigRelativePath(configurationRelativePath);

            bool? result = null;
            void DoCreate() => result = synchronousIOManager.CreateDirectory(path, cancellationToken);

            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
                if (systemIdentity == null)
                    await Task.Factory.StartNew(DoCreate, cancellationToken, TaskCreationOptions.LongRunning, TaskScheduler.Current).ConfigureAwait(false);
                else
                    await systemIdentity.RunImpersonated(DoCreate, cancellationToken).ConfigureAwait(false);

            return result.Value;
        }

        public Task StartAsync(CancellationToken cancellationToken) => EnsureDirectories(cancellationToken);

        public Task StopAsync(CancellationToken cancellationToken) => EnsureDirectories(cancellationToken);

        public async Task<bool> HandleEvent(EventType eventType, IEnumerable<string> parameters, CancellationToken cancellationToken)
        {
            await EnsureDirectories(cancellationToken).ConfigureAwait(false);

            if (!EventTypeScriptFileNameMap.TryGetValue(eventType, out var scriptName))
                return true;

            //always execute in serial
            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
            {
                var files = await ioManager.GetFilesWithExtension(EventScriptsSubdirectory, platformIdentifier.ScriptFileExtension, cancellationToken).ConfigureAwait(false);
                var resolvedScriptsDir = ioManager.ResolvePath(EventScriptsSubdirectory);

                foreach (var I in files.Select(x => ioManager.GetFileName(x)).Where(x => x.StartsWith(scriptName, StringComparison.Ordinal)))
                    using (var script = processExecutor.LaunchProcess(ioManager.ConcatPath(resolvedScriptsDir, I), resolvedScriptsDir, String.Join(' ', parameters), noShellExecute: true))
                    using (cancellationToken.Register(() => script.Terminate()))
                    {
                        var exitCode = await script.Lifetime.ConfigureAwait(false);
                        cancellationToken.ThrowIfCancellationRequested();
                        if (exitCode != 0)
                            return false;
                    }
            }
            return true;
        }

        public async Task<bool> DeleteDirectory(string configurationRelativePath, ISystemIdentity systemIdentity, CancellationToken cancellationToken)
        {
            await EnsureDirectories(cancellationToken).ConfigureAwait(false);
            var path = ValidateConfigRelativePath(configurationRelativePath);
            
            var result = false;
            using (await SemaphoreSlimContext.Lock(semaphore, cancellationToken).ConfigureAwait(false))
            {
                void CheckDeleteImpl() => result = synchronousIOManager.DeleteDirectory(path);

                if (systemIdentity != null)
                    await systemIdentity.RunImpersonated(CheckDeleteImpl, cancellationToken).ConfigureAwait(false);
                else
                    CheckDeleteImpl();
            }
            return result;
        }
    }
}